#include <iostream>
#include <stdio.h>

using namespace std;

int main() {
    
    int n;
    int n3 = 0;
    cin >> n;
    for(int i = 0;i <= n/5;i++){
        int n2 = n - i * 5;
        n3 += n2 / 2 + 1;
    }
    cout << n3;
    return 0;
}